Simple, low cost methods are needed to determine the effect of pesticides on non-target aquatic organisms. In this report, embryos of Paratanytarsus parthenogeneticus were exposed from deposition to hatch to five pesticides. Four of the five pesticides affected development or hatch only at coccentrations which exceeded 96-h LC50 values of other non-target invertebrates. One pesticide, fenitrothion, affected hatch at 13 micrograms/1 which is similar to 96-h LC50 values for other aquatic invertebrates. Because of the low sensitivity of the embryo to pesticides, this method may not be a useful pesticide screening test for non-target invertebrates.